Prismatic battery short circuit inspection method and prismatic battery manufacturing method

ABSTRACT

An object of the present invention is to easily detect a short circuit failure in a current collector of a prismatic battery and prevent a short circuit caused by an existence of a burr generated while cutting or a spatter generated while welding the current collector to an electrode plate. A battery unit is housed in a metallic battery case. In the battery unit, current collectors having bent portions on both sides are fixed to face surfaces of an electrode plate group of a prismatic battery. The portions of the battery case, which correspond to the bent portions, are pressed in a thickness direction. Under the pressure, a short circuit inspection for a short circuit between the battery case and the current collectors of the battery unit is executed. When a projected object exists on the bent portion, a short circuit is generated between the battery case and the current collector by pressing so that a short circuit failure caused by a shape of the current collector can be detected.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a short circuit inspection methodexecuting a short circuit inspection during a prismatic batterymanufacturing procedure to detect a short circuit caused by a shape of acurrent collector of a prismatic battery having an electrode plate groupcomposed of a positive electrode plate, negative electrode plate and aseparator, a prismatic battery manufacturing method including the shortcircuit inspection step, and a current collector shape adjusting deviceused in the prismatic battery manufacturing procedure to prevent a shortcircuit caused by a shape of the current collector.

2. Description of the Related Art

In recent years, portable information devices such as a cellular phone,note book-sized personal computer and so on have become widespread.Those devices aim for higher performance, reduced weight, andminiaturization. Accordingly, the secondary battery for use in the powersupply of the portable information devices is required to have reducedsize and weight and increased energy density. Further, such a secondarybattery is used as a driving power source of an electric vehicle or ahybrid electric vehicle.

Such a portable information device, electric vehicle, or hybrid electricvehicle has limited space to house the secondary battery. On the otherhand, the conventional secondary battery often has a cylindrical shapeand thus undesirably creates a gap in the limited space so that a largespace is required when it is housed.

Hence, in place of the cylindrical battery, a prismatic battery hasbecome mainstream as a secondary battery used in the above devices orvehicles. Such a prismatic battery has an electrode plate group 10, inwhich side edge portions of positive electrode plates 18 and negativeelectrode plates 19 stacked via separators 17 on the opposite sides areprotruded from facing areas of the both electrode plates, as shown inFIGS. 11A and 11B, and current collectors 20 are fixed to the protrudedportions (lead portions 18 a, 19 a) in both side areas of the electrodeplate group 10. Concretely, lead portion joint surfaces 24 of thecurrent collector 20 face the lead portions 18 a, 19 a, bent portions21, 21, bent from side ends of the respective lead portion jointsurfaces 24 are formed to lie over outer surfaces of the electrode plategroup 10 in a stack direction of the positive electrode plates 18 andnegative electrode plates 19, and at least a part of the respective leadportion joint surface 24 is welded and fixed to the lead portions 18 a,19 a. Further, an outer insulating tape 16 is attached on the outersurfaces of the positive electrode plate 18 and negative electrode plate19 between the bent portions 21, 21 to insulate from the battery case30.

When the current collectors 20 are fixed, the electrode plate group 10is housed in the battery case 30, as a battery unit. The size of thebattery case 30 is made close to the outside dimension of the electrodeplate group 10 since it influences the outside dimension of theprismatic battery.

Regarding such a prismatic battery, the electrode plate group 10 isgenerally inspected whether or not a short circuit is generated in theelectrode plate group 10 with the current collectors 20 before theelectrode plate group 10 is housed in the battery case 30, as disclosedin Patent Document 1.

[Patent Document 1] Japanese Patent Application Laid-Open No.2001-236985

Patent Document 1 describes a technique of “A short circuit inspectionmethod for a battery, in which an electrode plate group composed ofpositive electrode plates and negative electrode plates stacked viaseparators is inserted in a battery case, wherein a short circuitfailure is inspected while applying pressure on the electrode plategroup before inserting the electrode plate group into the battery case.”This technique is made in view of a short circuit failure caused by aswelling in the electrode plate group 10 by charges and discharges ofthe secondary battery, and the short circuit inspection is executedwhile applying pressure on a center portion of the electrode plate group10 in a stack direction of the positive electrode plates and thenegative electrode plates to virtually create a swelling condition.

Patent Document 2 proposes a technique for reducing a thickness of acircumference of a cut electrode plate to suppress an occurrence ofburrs, which cause a short circuit.

[Patent Document 2] Japanese Patent Application Laid-Open No. 8-45500

SUMMARY OF THE INVENTION

As described above, in the electrode plate group 10 for the prismaticbattery, current collectors 20 are provided at both ends and leadportion joint surfaces 24 of the current collectors 20 are fixed to thelead portions 18 a, 19 a of the electrode plate group 10 by an electronbeam welding. Generally, the lead portions 18 a, 19 a are welded atportions along the width direction of the current collector 20 withproper intervals in a longitudinal direction of the current collector 20(that is, a vertical direction of the current collector 20 in FIG. 11A).Then, a current collector insulating tape 40 is attached on the bentportions 21 and the electrode plate group 10 is housed in the batterycase 30.

There is no problem when the bent portions 21 of the current collector20 are flat, as shown in FIG. 10A; however, a projected object 29sometimes exists, as shown in FIG. 10B. The projected object 29 is, forexample, a spatter attached while welding or a burr generated whilecutting the current collectors 20 prior to the welding. The projectedobject 29 remained on the bent portion 21 of the current collector 20can break through the current collector insulating tape 40 insulatingbetween the battery case 30 and the bent portions 21 of the currentcollectors 20. This causes a short circuit between the current collector20 and the battery case 30.

However, the technique of Patent Document 1 is a short circuitinspection by applying pressure on a center portion of the electrodeplate group in a stack direction of the electrode plates and thepressure is not applied sufficiently to the bent portions of the currentcollectors, which are located in end portions of the electrode plategroup. As a result, even when a projected portion such as a burr and aspatter exists, the current collector insulating tape is not broken by aprojected portion and such an electrode plate group 10 is not detectedas a short circuit failure.

On the other hand, the technique of Patent Document 2 describes areduction of a thickness of a circumference of each electrode plate;however, it does not disclose a method for processing a projected objectsuch as a burr or a spatter generated on a current collector to bewelded to an electrode plate group. Further, since the technique is toreduce the thickness of the circumference of each electrode plate beforewelding, it is not effective for a matter of a spatter generated whilewelding.

The present invention is made in view of the above problems and has anobject to provide a prismatic battery short circuit inspection methodfor detecting a short circuit failure caused by an existence of aprojected object on a bent portion of a current collector, which is, forexample, a burr while cutting a current collector, a spatter whilewelding the current collector to an electrode plate, or a bulge causedby a deteriorated mold. Another object of the present invention is toprovide a prismatic battery manufacturing method including the shortcircuit inspection step, and further, a current collector shapeadjusting step to reduce short circuit failures. Another object of thepresent invention is to provide a current collector shape adjustingdevice capable of preventing a short circuit caused by a shape of thecurrent collector.

As a means for solving the above problem, the present applicationdiscloses the following invention. That is, a prismatic battery shortcircuit inspection method of the present invention is a method executinga short circuit inspection of a prismatic battery,

the prismatic battery having a battery unit comprising:

an electrode plate group; and

current collectors having lead portion joint surfaces, which arerespectively provided corresponding to lead portions of positiveelectrode plates and negative electrode plates in sides of the electrodeplate group, face to end portions of the lead portions, and have atleast a part to be welded and fixed to the lead portions, and bentportions bend from side edges of respective lead portion joint surfacesto lie over outer surfaces of the electrode plate group in a stackdirection of the positive electrode plates and the negative electrodeplates, and

the method comprising:

pressing portions on outer faces of a battery case, which arecorresponding to the bent portions facing each other in a manner ofsandwiching the electrode plate group therebetween, toward the stackdirection of the electrode plate group, in a condition that the batteryunit is housed in the battery case; and

executing a short circuit inspection between the battery case and thecurrent collector under the pressure.

Preferably, in the short circuit inspection, pressing plates havingpressure portions corresponding to positions where the bent portions areformed are provided in both sides of the battery case in a sandwichingmanner and the pressing plates are moved to be close to each other toapply pressure on the outer faces of the battery case to execute theshort circuit inspection.

A prismatic battery manufacturing method of the present invention is amethod manufacturing a prismatic battery,

the prismatic battery having a battery unit comprising:

an electrode plate group; and

current collectors having lead portion joint surfaces, which arerespectively provided corresponding to lead portions of positiveelectrode plates and negative electrode plates in sides of the electrodeplate group, face to end portions of the lead portions, and have atleast a part to be welded and fixed to the lead portions, and bentportions bend from side edges of respective lead portion joint surfacesto lie over outer surfaces of the electrode plate group in a stackdirection of the positive electrode plates and the negative electrodeplates, and

the method comprising:

housing the battery unit in a battery case;

applying, thereafter, pressure on portions on outer faces of the batterycase, corresponding to the bent portions facing each other in a mannerof sandwiching the electrode plate group therebetween, in a direction ofa thickness of the battery case; and

executing a short circuit inspection between the battery case and thecurrent collector under the pressure.

Preferably, in the short circuit inspection step, pressing plates havingpressure portions corresponding to positions where the bent portions areformed are provided in both sides of the battery case in a sandwichingmanner and the pressing plates are moved to be close to each other toapply pressure on the outer faces of the battery case to execute theshort circuit inspection.

The battery case can be a rectangular parallelepiped shape including anarrow side face and a wide side face, and the electrode plate groupcomprises a structure, in which a plurality of positive electrode platesand negative electrode plates are stacked with separators interposedtherebetween in a manner of being substantially parallel to the wideside face of the battery case, ends of the positive electrode platesprotrude outwardly from facing areas of the both electrode plates in oneside of the electrode plate group, ends of the negative electrode platesprotrude outwardly from the facing areas of the both electrode plates inthe other side of the electrode plate group, and the protruded ends ofthe both electrode plates serve as the lead portions.

Preferably, the battery unit is housed in a battery case after putting acurrent collector insulating tape at least on the current collectorwhich has a polarity opposite to the battery case out of the currentcollectors provided corresponding to each lead portion of the positiveelectrode plate and negative electrode plate.

The method can further have a step of applying an electrolyte into thebattery case after housing the battery unit in the battery case. Themethod can further have a step of activating the battery after theelectrolyte applying step. The method can further have a step of forminga module by assembling the battery case after housing the battery unitin the battery case and the short circuit inspection can be executed onthe formed module.

Preferably, the prismatic battery manufacturing method of the presentinvention has a step of adjusting a shape of the bent portion of thecurrent collector before housing the battery unit in the battery case.The shape adjusting step preferably has a step of pressing the bentportion of the current collector from both sides of the battery unit ina thickness direction to squash a projected object generated on the bentportion.

Preferably, after the shape adjusting step, the method further has stepsof measuring a height of the projected object, and determining whetheror not the height of the projected object obtained in the measuring stepis a height within an allowable range. In the determining step,preferably, an average value of heights of projected objects is obtainedand the height of the projected object to be determined is determinedwhether to be included within the allowable range, which is a rangeincluding the average value as a center value.

A current collector shape adjusting device of the present invention is adevice adjusting current collectors of a battery unit applied to aprismatic battery,

the battery unit comprising:

an electrode plate group; and

the current collectors having lead portion joint surfaces, which arerespectively provided corresponding to lead portions of positiveelectrode plates and negative electrode plates in sides of the electrodeplate group, face to end portions of the lead portions, and have atleast a part to be welded and fixed to the lead portions, and bentportions bend from side edges of respective lead portion joint surfacesto lie over outer surfaces of the electrode plate group in a stackdirection of the positive electrode plates and the negative electrodeplates, and

the current collector shape adjusting device comprising:

a work placement unit on which the battery unit is placed;

a pair of pressing pieces provided in both sides of the battery unit ina thickness direction to press and deform, in the thickness direction,the bent portions of the current collectors of the battery unit disposedon said work placement unit;

a pair of piece fixing plates fixing and supporting said respectivepressing pieces; and

a moving mechanism moving said pair of piece fixing plates and pressingpieces toward the battery unit placed on said work placement unit.

Preferably, each of the pressing piece has a head portion contactingwith the bent portion of the current collector, a main body fixed to thepiece fixing plate, and an elastic member disposed between the headportion and the main body.

Effect of the Invention

According to the prismatic battery short circuit inspection method andmanufacturing method of the present invention, pressure is applied tothe portions corresponding to the bent portions of the currentcollectors, which face each other as sandwiching the electrode plategroup therebetween, on the outer faces of the battery case in a stackdirection of the electrode plate group, in a condition that the batteryunit including the electrode plate group and current collectors ishoused in the battery case, and the short circuit inspection is executedunder the pressure. When a projected object exists on the bent portionand pressure is applied, the projected object can break through thecurrent collector insulating tape so that a short circuit is generatedbetween the battery case and the current collector. Accordingly, a shortcircuit failure caused by a shape of the current collector can bedetected.

Further, since the method includes a shape adjusting step for deforminga projected object generated on the bent portion of the currentcollector, an occurrence of short circuit failure can be suppressed andyield of the product can be improved.

Further, according to the current collector shape adjusting device ofthe present invention, since the projected object generated on the bentportion of the current collector can be deformed by pressing, anoccurrence of short circuit failure can be suppressed and yield of theproduct can be improved when the shape of the current collector isadjusted by using the current collector shape adjusting device beforehousing the battery unit in the battery case.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A to 1E are views used to explain a short circuit inspectionmethod;

FIGS. 2A to 2C are views showing a procedure for assembling a prismaticbattery, with FIG. 2A being a perspective view showing a side where acurrent collector insulating tape is attached, FIG. 2B being aperspective view showing a side where the current collector insulatingtape is not attached, and FIG. 2C being a perspective view showing astate of a module in which three battery cases are assembled;

FIG. 3 is a perspective view showing a current collector shape adjustingdevice;

FIG. 4A is a plan view showing the current collector shape adjustingdevice, and FIG. 4B is a side view of the current collector shapeadjusting device;

FIGS. 5A to 5C are views used to explain an operation of the currentcollector shape adjusting device, with FIG. 5A showing a movement of apressing piece and the like as seen from a plane direction, FIG. 5Bshowing the movement of the pressing piece and the like as seen from alateral direction, and with FIG. 5C being a enlarged view of a relevantpart of the pressing piece;

FIGS. 6A and 6B are views used to explain an outline of a measuringdevice;

FIG. 7A is a plan view showing a dimension measuring device used in ameasuring device, and FIG. 7B is a perspective view of the dimensionmeasuring device;

FIGS. 8A to 8C are plan views showing usage states of the dimensionmeasuring device;

FIGS. 9A to 9C are flowcharts to explain a height determination step ina determination device, which receives a measuring result from thedimension measuring device;

FIGS. 10A and 10B are sectional views showing a relation of a currentcollectors, a battery case and a spatter in the prismatic battery, withFIG. 10A showing a normal state, and FIG. 10B showing a state, in whicha projected object exists on a bent portion; and

FIG. 11A is a perspective view showing a typical configuration of anelectrode plate group of the prismatic battery, and FIG. 11B is a planview of the typical configuration of the electrode plate group.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

Embodiments of the present invention will be described with reference tothe drawings, taking a nickel-metal hydride battery as an example. FIGS.1A to 1E are views used to explain a short circuit inspection method andFIGS. 2A to 2C are views used to explain an assembly procedure of aprismatic battery. FIGS. 3 to 5C are views used to explain a currentcollector shape adjusting device for preventing a short circuit. FIGS.6A to 8C are views used to explain a measuring device inspecting apresence of a projected object such as a burr or a spatter and adimension measuring device provided to the measuring device. FIGS. 9A to9C are views used to explain determining steps.

First Embodiment

As shown in FIGS. 1A and 1B, current collectors 20 (which is made ofnickel-plated steel plate) are respectively provided corresponding tolead portions 18 a, 19 a (see FIGS. 11A and 11B), which are located inboth sides of an electrode plate group 10 used for a prismatic batteryin a rectangular parallelepiped shape. Each of the current collectors 20includes a lead portion joint surface 24 facing to an end portion of thelead portion 18 a, 19 a of the electrode plate group 10 and bentportions 21 bent from both ends of the lead portion joint surface 24 tolie over outer surfaces facing each other in a stack direction ofpositive electrode plates 18 and a negative electrode plates 19(thickness direction of the electrode plate group 10). Then, the leadportion joint surface 24 is welded to the end portion of the leadportion 18 a, 19 a. Here, a reference number 24 a shown in FIG. 1Arepresents welding lines formed on the lead portion joint surface 24.

As shown in FIGS. 1B and 2A, a current collector insulating tape 40 isattached on the current collector 20 in a positive electrode side, whichis welded to the lead portion of a positive electrode plate. The currentcollector insulating tape 40 is required to be attached at least on thecurrent collector 20 in the positive electrode side and can also beattached on the current collector 20 in a negative electrode side.

As shown in FIGS. 1A, 1B, 2A and 2B, an outer insulating tape 16 isattached on the outer surfaces of the electrode plate group 10.Concretely, the outer insulating tape 16 is attached around to cover allover the positive electrode plate 18 and negative electrode plate 19,which are located in an outermost of the electrode plate group 10.Further, on the electrode plate group 10, to which the outer insulatingtape 16 is attached, the current collector insulating tape 40 isattached at least on the current collector 20 in the positive electrodeside including the bent portions 21 thereof, as described above. Here, areference number 40 a in FIG. 1A represents opening portions to exposeterminal portions 20 a of the current collector 20.

As described above, the electrode plate group 10 is composed of theplurality of square-shaped positive electrode plates 18 and negativeelectrode plates 19 stacked via separators 17 and side edge portions ofthe electrode plates 18, 19 on the opposite sides are protruded fromfacing areas of both the electrode plates (see FIGS. 11A and 11B). Then,when the electrode plate group 10 and the current collector 20 are fixedto each other, the lead portions 18 a, 19 a of the electrode plate group10 are held by the bent portions 21 in a sandwiched manner. Thisprevents that the electrode plates 18, 19 spread out of the currentcollectors 20.

The outer insulating tape 16 is put on the outer surfaces of thepositive electrode plate 18 and negative electrode plate 19 between thebent portions 21 to insulate from the battery case 30, as describedabove, and the current collector 20 including the bent portions 21 ishoused in the battery case 30, with the current collector insulatingtape 40 therearound as shown in FIG. 1C. The battery case 30 (made ofnickel-plated steel plate) has wide side faces, which are substantiallyparallel to the positive electrode plates 18 and negative electrodeplates 19, and narrow side faces, which are faced to the currentcollector 20, and is negatively charged.

The battery unit having the electrode plate group 10 and currentcollectors 20 is housed in the battery case 30 and, in such a condition,a short circuit inspection is executed. According to the presentembodiment, as shown in FIGS. 1D and 1E, pressure portions 61, 61, whichare end portions of a pressing plate 60 having a U-shaped cross section,are attached to the outer faces of the battery case 30 locatedcorresponding to the bent portions 21, 21 to apply pressure to the bentportions 21 of the current collectors 20. Further, while applying thepressure, a short circuit inspection for measuring an insulationresistance is performed by putting a terminal of a short circuitinspection device (MΩ tester) 50 to contact with the terminal portion 20a of the current collector 20 in the positive electrode side, which isconnected to the lead portion 18 a of the positive electrode plate 18,and the battery case 30.

On the bent portions 21 of the current collector 20, a projected object29 such as a burr can be generated when the current collector 20 is cutin a predetermined size, a spatter can be caused when the currentcollector 20 is welded to the electrode plate group 10, or a bulgecaused by a deteriorated mold for forming the current collector 20 canexist (see FIG. 10B). Such a spatter is likely to be attached on thebent portion 21, particularly in unwelded portions 22, which are inextensions of the welding lines 24 a (hereinafter, referred to aswelding line correspondent portions 22), since the lead portions 18 a,19 a and the lead portion joint surfaces 24 of the current collectors 20are welded in width direction of the current collector 20.

Existence of such a projected object 29 like a burr and a spatter causesa short circuit during a short circuit inspection since the projectedobject 29 breaks through the current collector insulating tape 40 whenthe pressure portions 61 of the pressing plate 60 are attached the outerfaces of the battery case 30 and pressure is applied. Accordingly,battery units, which are hardly determined as defective productaccording to a conventional short circuit inspection method (forexample, a technique disclosed in Patent Document 1: Japanese PatentApplication Laid-Open No. 2001-236985) can be distinguished as defectiveproducts.

The above embodiment shows an example, in which the current collectorinsulating tape 40 is put on at least the current collector 20 in thepositive electrode side. However, the above short circuit inspection canbe used when an insulation coating is provided inside of the metallicbattery case 30, instead of putting the current collector insulatingtape 40 on the current collector 20.

As described above, the short circuit inspection of the presentembodiment is executed without applying electrolyte after the batteryunit is housed in the battery case 30. However, the short circuitinspection can be executed after housing the battery unit in the batterycase 30, and further, applying electrolyte to the battery case 30. Withthis procedure using the electrolyte, the short circuit inspection canbe executed in a condition assuming that the battery case 30 is actuallyinstalled in a device, compared to the case without applying theelectrolyte.

Further, an activating step for activating the battery is performedafter the electrolyte application step, and a module assembling step forassembling a module combining the battery cases 30 as shown in FIG. 2Cis performed after the activating step. Then, the short circuitinspection can be implemented on the assembled module. In this case, themodule can be assembled prior to the solution applying step andactivating step, and then, the short circuit inspection can be executedafter the solution applying step and activating step. Here, when themodule is assembled and internal resistance values or terminal voltagesbefore and after the inspection are compared during the short circuitinspection step, a part of performance test can be performed at the sametime.

Second Embodiment

According to the first embodiment, a short circuit inspection inprismatic battery manufacturing is executed by pressing the bentportions 21 of current collectors 20 to detect a short-circuit failurecaused by a projected object 29 generated on the bent portions 21.However, in order to improve yield, preferably, the present inventionhas not only a structure for detecting a battery unit having a currentcollector 20 with a projected object 29 as a failure but also astructure for deforming the projected object 29 into a size within apredetermined size before executing the short circuit inspection. Withsuch a structure, a short circuit failure caused by a projected object29 breaking through the current collector insulating tape 40 can bereduced.

The shape adjusting step can be performed for all bent portions 21 ofcurrent collectors 20 regardless of the presence or absence of aprojected object 29 or can be performed for only bent portions 21, onwhich a projected object 29 is detected. Further, in the case that aprojected object 29 is detected, the shape adjusting step can beperformed only when the height of the projected object 29 excesses anallowable range. Accordingly, in this case, it is required to measurewhether or not the height of the projected object 29 is within theallowable range before the shape adjustment. Here, such a measurementcan be performed by a measuring device 90, which is generally used for aheight confirmation inspection of projected objects 29 after shapeadjustment. The details in the measurement method will be describedlater.

The shape adjusting step is a step for adjusting the shape of the bentportions 21 of the current collectors 20. The shape adjusting step isperformed by a current collector shape adjusting device 70 shown inFIGS. 3 to 5C before housing a battery unit having an electrode plategroup 10 and current collectors 20 in a battery case 30, and morepreferably, before putting the current collector insulating tape 40 tothe current collectors 20. The current collector shape adjusting device70 includes a work placement unit 71, pressing pieces 72, piece fixingplates 73 and a moving mechanism.

The work placement unit 71 is formed with a mounting member, to whichthe battery unit having the electrode plate group 10 with the currentcollectors 20 is placed. The pressing pieces 72 is provided in bothsides of the battery unit in its thickness direction to sandwich thebattery unit placed on the work placement unit 71. A plurality ofpressing pieces 72 are provided in both sides of the battery unit in itsthickness direction in parallel. The number of the pressing pieces 72 tobe arranged in parallel is not limited; however, as shown in FIG. 4A,for example, the pressing pieces 72 are respectively providedcorresponding to the positions of the welding line correspondentportions 22 on the bent portions 21 of the current collector 20. Thepressing pieces 72 can be provided corresponding to adjacent portions 23on the bent portions 21, which are adjacent to the welding linecorrespondent portion 22. As described above, a spatter is oftenattached to the welding line correspondent portions 22 but sometimesattached to the adjacent portions 23. Also, a bulge caused by adeteriorated mold can be generated at the adjacent portions 23, additionto the welding line correspondent portions 22.

The piece fixing plates 73 fix and support the pressing pieces 72provided in a manner of sandwiching the battery unit (work placementunit 71), and a pair of piece fixing plates 73 are provided in a mannerof sandwiching the work placement unit 71. Each of the piece fixingplates 73 is supported by the moving mechanism, and moved, by the movingmechanism, toward the battery unit placed on the work placement unit 71to press the bent portion 21 with the respective pressing pieces 72. Themoving mechanism includes sliders 73A respectively provided on the lowerface of the piece fixing plates 73, rails 74 to which each of thesliders 73A are engaged to slide thereon, a pair of pressure arms 75,which are substantially L-shaped and provided corresponding to each ofthe piece fixing plates 73 to press the rear edges 73B of the piecefixing plates 73 toward the battery unit, and a pressure cylinder 76having a piston 76A and a cylinder 76B. The piston 76A is connected toone of the pressure arms 75 and the cylinder 76B is connected to theother of the pressure arms 75. The distance between the pressure arms75, 75 are adjusted by the piston 76A, which moves forwardly andbackwardly relative to the cylinder 76B. Accordingly, when both of thepressure arms 75, 75 are moved to be close to each other, each of thepressing pieces 72, 72 supported by the piece fixing plates 73, 73 aremoved toward the battery unit (see FIG. 5B).

As shown in FIGS. 4A to 5C, each of the pressing pieces 72 has a headportion 72A made of iron or steel at its end and the head portion 72A issupported by a main body 72C fixed to the piece fixing plate 73 via aspring 72B as an elastic member. Accordingly, as shown in FIG. 5C, whenthe pressing pieces 72 presses bent portions 21, 21, one of which has aprojected object 29, from both sides of the battery unit, the reactionforce under the pressure can be adjusted by the springs 72B provided tothe pressing pieces 72 facing each other. Thus, the bent portions 21 canbe pressed equally from both sides.

An operation of the current collector shape adjusting device 70 will bedescribed. For example, as shown in FIG. 5C, it is assumed that aprojected object 29 caused by a spatter is attached on a welding linecorrespondent portion 22 of the bent portion 21 of the current collector20. The battery unit having the projected object 29 is placed on thework placement unit 71 and the pressure cylinder 76 is run. Since thepressure cylinder 76 presses the piece fixing plates 73 via the pressurearms 75 toward the battery unit, the pressing pieces 72, 72 fixed to thepiece fixing plates 73, 73 apply pressure on the bent portions 21, 21 ofthe current collector 20 of the battery unit from both sides, asindicated by the imaginary lines in FIG. 5B. With this procedure, theprojected object 29 is squashed and deformed. As a result, there is nomore projected object 29 or the height of the projected object 29becomes less than the predetermined size. Accordingly, when a currentcollector insulating tape 40 is put on the current collector 20, thecurrent collector insulating tape 40 is hardly broken by the projectedobject 29 and short circuit failures of the current collector 20 andbattery case 30 can be suppressed.

After the shapes of the bent portions 21 of the current collector 20 areadjusted by the current collector shape adjusting device 70, aninspection is executed to check whether or not a projected object 29,which excess the allowable range, remains on the shape-adjusted bentportions 21. This inspection is executed by measuring the height ofprojected objects 29 on the bent portion 21. The height of projectedobject 29 is measured by the measuring device 90 shown in FIGS. 6A and6B. The measuring device 90 has a placement unit (not shown) for placingthe battery unit having the electrode plate group 10 and currentcollector 20 and dimension measuring devices 80 are provided in a mannerof sandwiching the placement unit. As shown in FIGS. 6A and 6B, thedimension measuring devices 80 are provided in positions indicated by Ato E and A′ to E′ in both sides of the battery unit, corresponding tothe five welding line correspondent portions 22 in one side (that is,ten positions in both sides) on the bent portions 21 of the currentcollector 20. Further, data measured by the respective dimensionmeasuring devices 80 are sent to a determination device 87 to determinewhether or not a projected object 29 still exists and, when exists,whether or not the height of the projected object 29 is included theallowable range.

As shown in FIGS. 7A and 7B, each of the respective dimension measuringdevices 80 includes a slider 82 slidable along a rail member 81, a block83, which has a U-shaped horizontal cross section and fixed to theslider 82, a cylindrical measuring base 84 housed in an opening of theblock 83 and a measuring head 85, which is extendable from the openingof the block 83 in an axial direction of the cylinder of the measuringbase 84 and moves forward and backward in the axial direction of themeasuring base 84.

The dimension measuring devices 80 in the positions indicated by A to Eand A′ to E′ move toward each other along the rail member 81 (not shownin FIGS. 6A and 6B), as from the state shown in FIG. 6A to the stateshown in FIG. 6B. The dimension measuring devices 80 stop moving whenbeing close to the bent portion 21 in some level. Then, the measurementsof the respective welding line correspondent portions 22 are performedby the respective dimension measuring devices 80 in the positions A to Eand A′ to E′. Here, since this movement is only an example, the devices80 in the positions A to E and the devices 80 in positions A′ to E′ donot have to move together and can move separately.

As described above, when the dimension measuring devices 80 are movedclose to the bent portions 21, front end surfaces 83 a of the block 83are attached to both sides of the welding line correspondent portion 22of the bent portion 21, as shown in FIG. 8A. Then, the measuring head 85is operated. As shown in FIG. 8A, when there is no projected object 29such as a burr or a spatter, the measuring head 85 projects to the samelevel of the front end surfaces 83 a of the block 83 and stops moving.That is, there is no difference in the levels of the attachment surfaceof the measuring head 85 and the front end surfaces 83 a of the block83. This data is sent to the determination device 87; however, since thedifference is “0,” it is determined that the height of a projectedobject 29 in the measured portion is within the allowable range, or thatthere is no projected object 29 in the portion.

On the other hand, as shown in FIG. 8B, when a projected object 29 isformed by a spatter on the bent portion 21 of the welding linecorrespondent portion 22 of the current collector 20, the measuring head85 contacts with the projected object 29 made of a spatter and cannotproject to the same level of the front end surfaces 83 a of the block83. Accordingly, a difference is generated between the levels of themeasuring head 85 and the front end surfaces 83 a. The difference in thelevels is sent to the determination device 87 to determine whether ornot the difference is within the allowable range. The procedure proceedsto a following step only when the difference is within the allowablerange. When the difference excesses the allowable range, the batteryunit is discarded, or the shape adjustment by the current collectorshape adjusting device 70 for the current collector 20 can be repeateduntil the difference becomes the level of the allowable range.

FIG. 8C shows a case that a projected object 29 exists on the adjacentportion 23 adjacent to the welding line correspondent portion 22 on thebent portion 21. On the adjacent portion 23, also, a spatter generatedduring a welding process can be attached, a burr remains, or a bulgecaused by an age-deteriorated mold for manufacturing the currentcollector 20 can be generated. When such a projected object 29 exits onthe adjacent portion 23, the front end surface 83 a of the block 83contact with the projected object 29 on the adjacent portion 23.Accordingly, a difference between the front end surface 83 a and themeasuring head 85 is generated and the determination device 87determines whether or not the difference is within the allowable range.

Although the projected object 29 on the adjacent portion 23 can bemeasured as shown in FIG. 8C, if the block 83, measuring base 84 andmeasuring head 85 are movable in a direction orthogonal to the railmember 81, the measuring head 85 is attached to the projected object 29on the adjacent portion 23 and the distance between the measuring head85 and the front end surface 83 a of the block 83 can be measured,similar to the case of FIG. 8B. Further, a set of the five dimensionmeasuring devices 80 in the positions A to E and a corresponding set ofthe five dimension measuring devices 80 in the positions A′ to E′ inFIGS. 6A and 6B can be made movable in a direction orthogonal to thedirection moving toward the battery unit to measure the height of theprojected object 29 on the adjacent portion 23.

A height determination step of the determination device 87, whichreceives measurement results from the dimension measuring devices 80,will be described with reference to FIGS. 9A to 9C. Firstly, the heightof the projected object 29 on the welding line correspondent portion 22of the bent portion 21 is measured. For example, as shown in FIGS. 6Aand 6B, the measurement is performed on the ten welding linecorrespondent portions 22 (S101) and, among the measurements, themeasured value from the dimension measuring device 80 in the position E′is referred to as A1 (S102). The measured value A1 is relevant to thedifference in the levels of the measuring head 85 and the front endsurface 83 a of the block 83, shown in FIG. 8B. When the measured valueA1 is simply applied and, for example, the value A1 is between apredetermined upper limited value and a predetermined lower limitedvalue, it is determined that the height is within the allowable range.In this case, when the bent portions 21 are formed completely the samein every battery unit, it is not a case to be concerned. However, themeasured value A1 is the difference in levels of the measuring head 85and the front end surfaces 83 a of the block 83, that is, a relativedisplacement amount thereof. The bent portion 21 itself can haveirregularities and deformations on its surface caused by anage-deteriorated mold for manufacturing current collectors 20,regardless of projected objects 29. In this case, when a projectedobject 29 of one battery unit and a projected object 29 on anotherbattery unit are compared, the measured values A1 as relativedisplacement amounts between the measuring head 85 and the front endsurface 83 a of the block 83 can be differ in every battery unit even ifthe heights of the projected object 29 itself are the same. Thus, whenthe upper limited value and lower limited value of the allowable rangeare determined without variations, this can reduce the accuracy ofdetermination results.

Accordingly, a shown in FIG. 9C, it is preferable to obtain an averagevalue by averaging the measured values at the welding line correspondentportions 22 more than once and to determine whether or not the measuredvalue A1 is within the allowable range, with respect to the averagevalue. The number of averaging can be arbitrarily determined; however,when a measured value, for example, a measured value A1, is newlyobtained, it is preferable to calculate an average value including thenewly obtained measured value A1. Concretely, assuming that the numberof averaging is 15, when the measured value A1 is newly obtained (S301),the oldest data among the former 15 values is deleted (S302), the newmeasured value A1 is added (S303), and an average value B1 in the new 15values is calculated (S304). Then, as shown in S103 in FIG. 9A, withrespect to the average value B1, an upper limited value C1 (for example,B1+80 μm) and a lower limited value D1 (for example, B1−80 μm) areobtained, an allowable range is determined, and then, it is determinedthe measured value A1 is within the allowable range (S104). When themeasured value A1 is within the allowable range, the procedure proceedsto an inspection step of the adjacent portions 23. When the measuredvalue A1 is out of the allowable range, the unit is discharged as adefective product.

On the other hand, since an age-deteriorated mold remarkably reduce theaccuracy of forming bent portion 21 in some cases, the average value B1calculated by including a new measured value can be increased ordecreased, compared to a former obtained average value B1. Accordingly,as shown in S305 in FIG. 9C, it is determined whether or not the newlycalculated average value B1 is within a predetermined reference valuerange and, when it is out of the reference value range, it is preferablenot to accept the battery unit. To determine the reference value range,some battery units are previously measured and an average value B1 andits standard deviation σ is obtained. Further, when a new average valuebased on the new measured value is obtained, its standard deviation σcan be newly obtained to update the reference value range sequentially(S306). Then, when it is confirmed that the new average value B1 isincluded in the reference value range, the procedure proceeds to S103 inFIG. 9A. Here, when the average value B1 is out of the reference valuerange, since the deformation of the current collector 20 is remarkable,an action such as stopping the equipment or the like is taken withoutcalculating a new reference value range (S307, S308).

In S104 of FIG. 9A, when measured values for all the welding linecorrespondent portions 22 are included in the allowable range, thedimension measuring device 80 measures heights of projected objects 29on the adjacent portions 23 (in the example of FIGS. 6A and 6B, theeight positions between the welding line correspondent portions 22)(S201). Accordingly, for example, when a measured value A2 is obtained(S202), the steps of S301 to S305 in FIG. 9C are performed using themeasured value A2, similar to the case of measured value A1 at thewelding line correspondent portion 22 to obtain an average value B2 forprojected objects on the adjacent portions 23 and to determine whetherthe average value B2 is within the reference value range. When theaverage value B2 is obtained and the average value B2 is included in thereference value range, an upper limited value C2 (for example, B2+80 μm)and a lower limited value D2 (for example, B2−80 μm) are calculated(S203) and it is determined whether or not the measured value A2 isincluded in a range between the upper limited value C2 and lower limitedvalue D2 (S204). When the measured value A2 is within the allowablerange, the procedure proceed a sequential step to put a currentcollector insulating tape 40 thereon or house the battery unit into abattery case 30 and the like. When the measured value A2 is out of theallowable range, the battery unit is discharged as a defective product.

INDUSTRIAL APPLICABILITY

The present invention is mainly applicable to fields of manufacturingprismatic batteries and inspecting prismatic batteries. As a secondarybattery, the present invention can be applied to a lithium-ion battery,nickel-metal hydride battery and the like. Further, the presentinvention is applied to a primary battery that is a prismatic battery.

1. A prismatic battery short circuit inspection method for executing ashort circuit inspection of a prismatic battery, the prismatic batteryhaving a battery unit comprising: an electrode plate group composed of aplurality of square-shaped positive electrode plates and negativeelectrode plates stacked via separators in which side edge portions ofthe electrode plates on the opposite sides are protruded from facingareas of both the electrode plates; and current collectors having leadportion joint surfaces, which are respectively provided corresponding tolead portions of positive electrode plates and negative electrode platesin sides of the electrode plate group, face end portions of the leadportions, and have at least a part to be welded and fixed to the leadportions, and bent portions bent from side edges of respective leadportion joint surfaces to lie over outer surfaces of the electrode plategroup in a stack direction of the positive electrode plates and thenegative electrode plates, and the method comprising: housing thebattery unit in a metallic battery case with an insulation resistanceintervening between the battery case and the bent portions in at leastthe current collector which has a polarity opposite to the battery case,applying pressure from outer surfaces of the battery case to positionscorresponding to the bent portions in at least the current collectorwhich has the polarity opposite to the battery case, so as to cause aprojected object to break through the insulation resistance between thebattery case and the bent portions when the projected object exists onthe bent portions; and executing a short circuit inspection between thebattery case and the current collector under the pressure.
 2. Theprismatic battery short circuit inspection method according to claim 1,wherein pressing plates having pressure portions corresponding topositions where the bent portions are formed are provided in both sidesof the battery case in a sandwiching manner and the pressing plates aremoved to be close to each other to apply pressure on the outer faces ofthe battery case to execute the short circuit inspection.
 3. A prismaticbattery manufacturing method for manufacturing a prismatic battery, theprismatic battery having a battery unit comprising: an electrode plategroup composed of a plurality of square-shaped positive electrode platesand negative electrode plates stacked via separators in which side edgeportions of the electrode plates on the opposite sides are protrudedfrom facing areas of both the electrode plates; and current collectorshaving lead portion joint surfaces, which are respectively providedcorresponding to lead portions of positive electrode plates and negativeelectrode plates in sides of the electrode plate group, face endportions of the lead portions, and have at least a part to be welded andfixed to the lead portions, and bent portions bent from side edges ofrespective lead portion joint surfaces to lie over outer surfaces of theelectrode plate group in a stack direction of the positive electrodeplates and the negative electrode plates, and the method comprising:housing the battery unit in a metallic battery case with an insulatingmaterial intervening between the battery case and the bent portions inat least the current collector which has a polarity opposite to thebattery case; applying, thereafter, pressure from outer surfaces of thebattery case to positions corresponding to the bent portions in at leastthe current collector which has the polarity opposite to the batterycase, so as to cause a projected object to break through the insulatingmaterial between the battery case and the bent portions when theprojected object exists on the bent portions; and executing a shortcircuit inspection between the battery case and the current collectorunder the pressure.
 4. The prismatic battery manufacturing methodaccording to claim 3, wherein, in said short circuit inspection step,pressing plates having pressure portions corresponding to positionswhere the bent portions are formed are provided in both sides of thebattery case in a sandwiching manner and the pressing plates are movedto be close to each other to apply pressure on the outer faces of thebattery case to execute the short circuit inspection.
 5. The prismaticbattery manufacturing method according to claim 3, wherein the batterycase is a rectangular parallelepiped shape including a narrow side faceand a wide side face, and wherein the electrode plate group comprises astructure, in which a plurality of positive electrode plates andnegative electrode plates are stacked with separators interposedtherebetween in a manner of being substantially parallel to the wideside face of the battery case, ends of the positive electrode platesprotrude outwardly from facing areas of the both electrode plates in oneside of the electrode plate group, ends of the negative electrode platesprotrude outwardly from the facing areas of the both electrode plates inthe other side of the electrode plate group, and the protruded ends ofthe both electrode plates serve as the lead portions.
 6. The prismaticbattery manufacturing method according to claim 3, wherein the batteryunit is housed in a battery case after putting a current collectorinsulating tape as the insulating material at least on the currentcollector which has a polarity opposite to the battery case out of thecurrent collectors provided corresponding to each lead portion of thepositive electrode plate and negative electrode plate.
 7. The prismaticbattery manufacturing method according to claim 3, further comprisingapplying an electrolyte into the battery case after housing the batteryunit in the battery case.
 8. The prismatic battery manufacturing methodaccording to claim 7, further comprising activating the battery aftersaid electrolyte applying step.
 9. The prismatic battery manufacturingmethod according to claim 3, further comprising forming a module byassembling the battery case after housing the battery unit in thebattery case, wherein the short circuit inspection is executed on theformed module.
 10. The prismatic battery manufacturing method accordingto claim 3, further comprising adjusting a shape of the bent portion ofthe current collector before housing the battery unit in the batterycase.
 11. The prismatic battery manufacturing method according to claim10, wherein said shape adjusting step comprises pressing the bentportion of the current collector from both sides of the battery unit ina thickness direction to squash a projected object generated on the bentportion.
 12. The prismatic battery manufacturing method according toclaim 11, further comprising, after said shape adjusting step, measuringa height of the projected object; and determining whether or not theheight of the projected object obtained in said measuring step is aheight within an allowable range.
 13. The prismatic batterymanufacturing method according to claim 12, wherein, in said determiningstep, an average value of heights of projected objects is obtained andthe height of the projected object to be determined is determinedwhether to be included within the allowable range, which is a rangeincluding the average value as a center value.